Grinding (abrasive cutting)

A wide variety of machines are used for grinding, best classified as portable or stationary: Milling practice is a large and diverse area of manufacturing and toolmaking.

It can produce very fine finishes and very accurate dimensions; yet in mass production contexts, it can also rough out large volumes of metal quite rapidly.

Compared to "regular" machining, it is usually better suited to taking very shallow cuts, such as reducing a shaft's diameter by half a thousandth of an inch or 12.7 μm.

Each grain of abrasive functions as a microscopic single-point cutting edge (although of high negative rake angle), and shears a tiny chip that is analogous to what would conventionally be called a "cut" chip (turning, milling, drilling, tapping, etc.)

The choice of grinding operation is determined by the size, shape, features and the desired production rate.

Normal grinding is used primarily to finish surfaces, but CFG is used for high rates of material removal, competing with milling and turning as a manufacturing process choice.

CFG has the disadvantage of a wheel that is constantly degrading, requires high spindle power (51 hp or 38 kW), and is limited in the length of part it can machine.

[1] To address the problem of wheel sharpness, continuous-dress creep-feed grinding (CDCF) was developed in 1970s.

[1] Peel grinding, patented under the name of Quickpoint in 1985 by Erwin Junker Maschinenfabrik, GmbH in Nordrach, Germany, uses a thin superabrasive grinding disk oriented almost parallel to a cylindrical workpiece and operates somewhat like a lathe turning tool.

[4] The surface grinder is composed of an abrasive wheel, a workholding device known as a chuck, either electromagnetic or vacuum, and a reciprocating table.

These all tend to clog the cutting wheel more than steel and cast iron, but can be ground with special techniques.

An ELID cell consists of a metal-bonded grinding wheel, a cathode electrode, a pulsed DC power supply, and electrolyte.

The dissolution of the metallic bond material is caused by the dressing which in turns results the continuous protrusion of new sharp grits.

It is generally made from a matrix of coarse abrasive particles pressed and bonded together to form a solid, circular shape; various profiles and cross-sections are available depending on the intended usage for the wheel.

Grinding wheels may also be made from a solid steel or aluminium disc with particles bonded to the surface.

Cast Iron and mild steel have very good characteristics for cylindrical grinding.

Chemical property changes include an increased susceptibility to corrosion because of high surface stress.

High grinding temperatures may cause a thin martensitic layer to form on the part, which will lead to reduced material strength from microcracks.